1. Technical Field
The present invention relates to MEMS devices, liquid ejecting heads, and liquid ejecting apparatuses, and particularly relates to ink jet recording heads and ink jet recording apparatuses that eject ink as a liquid.
2. Related Art
There is a liquid ejecting head, which is an example of a device including a MEMS (Micro Electro Mechanical Systems) device, that includes a flow channel formation substrate in which pressure generation chambers communicating with corresponding nozzle openings that eject a liquid are formed, piezoelectric actuators provided on one surface side of the flow channel formation substrate, a protective substrate bonded to the piezoelectric actuator side of the flow channel formation substrate, a driving circuit that drives the piezoelectric actuators, and a manifold that serves as a common liquid chamber for the pressure generation chambers.
The driving circuit is disposed on one surface of the protective substrate (called an “installation surface” hereinafter), and a terminal portion of the driving circuit is electrically connected to the piezoelectric actuators by bonding wires. Meanwhile, an interconnect pattern connected to external wiring such as an FPC or the like is formed on the installation surface of the protective substrate, and the interconnect pattern and the driving circuit are electrically connected by bonding wires.
The manifold is open on the installation surface side of the protective substrate, and that opening is sealed by a flexible compliance portion of a sealing substrate. This sealing substrate is bonded to a region of the installation surface where the interconnect pattern is not provided (for example, see JP-A-2004-17600).
In such a liquid ejecting head, the liquid is supplied to the manifold from an external liquid supply source, and the liquid is then supplied from the manifold to the respective pressure generation chambers. Predetermined driving waveforms are then applied to the piezoelectric actuators from the driving circuit, and the liquid within the pressure generation chambers is pressurized and ejected from the nozzle openings. Meanwhile, the compliance portion deforms so as to absorb pressure changes in the liquid within the manifold, and thus the pressure of the liquid within the manifold can be kept constant.
Here, if the sealing substrate is to be bonded to the protective substrate while avoiding the interconnect pattern, it is necessary to secure a region for the sealing substrate to be bonded to the protective substrate, which increases the size of the liquid ejecting head in a planar direction. Accordingly, a configuration can be considered in which, when viewed in plan view, both ends of the interconnect pattern to which the external wiring, bonding wires, or the like are connected are exposed, and the sealing substrate is bonded to the protective substrate so that the sealing substrate overlaps with the other regions. According to this configuration, part of the interconnect pattern can also function as a region to which the sealing substrate is bonded, and thus the bonding region of the protective substrate can be reduced in size, making it possible to reduce the size in the planar direction.
However, there is a risk that adhesive will enter into the interconnect pattern, the periphery thereof, and so on from between the sealing substrate and the protective substrate and reach the region where the bonding wires of the interconnect pattern are connected. If that region is covered by adhesive, there is a risk that the bonding wires can no longer be electrically connected and the piezoelectric actuator can no longer be driven correctly.
It should be noted that this problem is not limited to liquid ejecting heads that eject liquid, and also arises in the same manner in other MEMS devices aside from liquid ejecting heads.